Dutch Uselton Lennox Industries Inc. Van Baxter Oak Ridge National Lab

Transcription

1 Dutch Uselton Lennox Industries Inc. Van Baxter Oak Ridge National Lab

2 Overview Study to assess annual differences in : Operating cost Site energy consumption Primary energy consumption, and Greenhouse gas emissions (GHG) Between two common residential space conditioning systems in North America: Central Air Conditioner + Warm Air Natural Gas Furnace Electric Air-to-Air Heat Pump

3 Data Sources Residential site energy costs are taken from the US Dept. of Energy 2010 Residential Nationally-Averaged Energy Costs, published in the Congressional Federal Register $ per kwh for electricity consumed at site $ per kwh(t) for natural gas consumed at site

4 Data Sources, (continued) Factors for source energy and GHG emissions associated with site energy consumption come from Source Energy and Emission Factors for Energy Use in Buildings, M. Deru and P. Torcellini, This is National Renewable Energy Laboratory Report: NREL/TP

5 Data Sources, (continued) Heating and Cooling Equipment Performance (capacity & efficiency vs.- outdoor temperature) comes from AHRI certified equipment and, in the case of heat pumps, has been extended to properly represent operation for six defined climatological regions. The GHG Factor for refrigerant R410A* and the assumed equipment refrigerant leakage rate comes from a 2002 Arthur D. Little study: Global Comparitive Analysis of HFC and Alternative Technologies for Refrigeration, Air Conditioning, Foam, Solvent, Aerosol Propellant and Fire Protection Applications. *All vapor compression systems evaluated use R410A.

6 Data Sources, (continued) Six cities were chosen to represent each of the six climatological regions defined by the US DoE Test Procedure for Residential Central Air and Heat Pumps. Portland, OR Minneapolis, MN Indianapolis, IN Ft. Worth, TX Nashville, TN Orlando, FL

7 Data Sources, (continued) For AC + Gas Furnace: Northern cities used 13 SEER condensers and 90 AFUE furnaces Southern cities used 14 SEER condensers and 80 AFUE furnaces Heat Pumps were always 14 SEER / 8.5 HSPF (Region IV) Weather Data for the cities are from the 2009 edition of the ASHRAE Handbook of Fundamentals.

8 Annual Site Energy Consumption and Operating Costs for Gas Furnace + Central Air Conditioner Cooling City DOE Region Minimum SEER Corresponding Seasonal CCOP Cooling Load (kwh) Cooling Electrical Energy Use (kwh) Cooling Season Operating $0.115/kWh ($) Orlando I Ft. Worth II Nashville III Indianapolis IV Minneapolis V Portland VI Heating City DOE Region Min. AFUE Furnace Electrical Power (kw) Heating Load (kwh) Natural Gas HHV Fuel Input (kwh thermal) Heating Electrical Energy Use (kwh) Heating Season Op. $0.115/kWh & $ /kWh (thermal) Orlando I Ft. Worth II Nashville III Indianapolis IV Minneapolis V Portland VI

9 Annual Site Energy Consumption and Operating Costs for Heat Pump Cooling City Heating DOE Region SEER Cooling COP Cooling Load (kwh) Cooling Electrical Energy Use (kwh) Cooling Season Operating $0.115/kWh ($) Orlando I Ft. Worth II Nashville III Indianapolis VI Minneapolis V Portland VI City DOE Region Region IV (min DHR) HSPF Cooling Oversize Factor HSPF for mid- DHR, Region, Sizing Factor Heating COP Heating Load (kwh) Heating Electrical Energy Use (kwh) Heating Season Operating $0.115/ kwh ($) Orlando I Ft. Worth II Nashville III Indianapolis IV Minneapolis V Portland VI

10 The Continental US has three large electrical interconnects Western ERCOT (most of Texas) Eastern

11 Electricity generation fuel mix for US National (lower forty eight), AK, HI, and Regional averages.

12 Full-Fuel Cycle Losses Delivered electrical energy has inefficiencies and losses going back through the energy supply system. For this study, these losses are taken into account based upon the interconnect region: Pre-combustion loss Generation loss Transmission loss For natural gas energy delivery, there are also upstream losses. For this study, the same upstream loss (9%) is used for all sites.

13 For natural gas, a national average emission factor for residential furnace combustion of kg/m 3 (includes transmission, etc., losses to deliver the fuel to the building) was used for all sites in the present analysis.

14 For a particular state, it is difficult to know the electrical generation source. Many import a significant fraction of their electric power from neighboring states and/or Canada (varies with time of year). Average regional emission factors were used for each site in this analysis. CO 2e => sum of CO 2 and CO 2 equivalent emissions of CH 4 and N 2 O.

15 Annual Full-Fuel Cycle Energy for Two HVAC Alternatives in Six Cities kwh Source Energy Annually Gas + AC Heat Pump 0 Heat Pump has lowest primary energy consumption except for Indianapolis and Minneapolis.

16 Estimated Annual HVAC Operating Cost ($) "Gas + Elec. AC" "Heat Pump" Orlando 1 Ft. Worth 2 Nashville 3 Indianapolis 4 Minneapolis 5 Portland 6

17 CO 2e Emissions Over 15 Year Life kg CO2e Emissions As with primary energy, the heat pump is lowest in all cities except Indianapolis and Minneapolis. Black bar at top of columns represents GHG impact of R410A loss.

18 Comparison of Best HVAC Alternatives: Minneapolis, MN Annual Full-Fuel Cycle Energy Use (kwh thermal) gas/electric heat pump Estimated Annual Operating Cost ($) gas/electric heat pump CO 2e Emissions Over 15 Year Life (kgs) gas/electric heat pump Best Equipment Specifications: Gas Furnace + Electric AC 98 AFUE and 13 SEER (3.8 cooling SPF) 2 Stage Heat Pump 8.42 Region V HSPF and 17.4 SEER (2.47 & 5.10 heating & cooling SPFs, respectively) - HP was oversized: ~17.5kW nominal cooling capacity at high capacity stage only 1 st (low) stage capacity used for space cooling

19 Concluding Observations Study purpose was to assess annual differences in annual operating costs, energy consumption and CO 2e emissions between two of the most commonly used residential space conditioning systems in North America: Central Air Conditioner + Warm Air Natural Gas Furnace Electric Air-to-Air Heat Pump For baseline efficiency options: the heat pump option has the advantage in Portland, Ft. Worth, Nashville, and Orlando (milder winter climates); the gas/ac option has slightly better source energy and CO 2e emission performance and the heat pump slightly lower operating cost in Indianapolis (Region IV); and the gas/ac option has the advantage in Minneapolis (cold climate) For Best efficiency options in Minneapolis - The two-stage heat pump has slightly lower operating cost and the gas/ac slightly lower source energy use and CO 2e emissions An increase in heating SPF to 2.9 (~17% improvement) would enable the heat pump to achieve equal CO 2e emissions and lower energy use than the gas/ac option both capacity and efficiency boost options should be investigated to improve low temperature performance for the heat pump